Cellulosic fibers such as paper pulp, bagasse, insulation or fiber board materials, cotton and the like, are commonly subjected to a refining operation which consists of mechanically rubbing the fiber between sets of relatively rotating bar and groove elements. In a disk-type refiner, for example, these elements commonly consist of plates having annularly arranged bar and groove patterns defining their working surfaces, with the bars and grooves extending generally radially of the axis of the rotating element, or more often at an angle to a radius to the center of the annular pattern, so that the stock can work its way from the center of the pattern to its outer periphery.
Disk-refiners are commonly manufactured in both single and twin disk types. In the former, the working surface of the rotor comprises an annular refiner plate, or a set of segmental refiner plates, for cooperative working action with a complementary working surface on the stator which also comprises an annular plate or a series of segmental plates forming an annulus. In a twin disk refiner, the rotor is provided with working surfaces on both sides which cooperate with a pair of opposed complementary working surfaces on the stator, with these working surfaces being of the same type of construction as with a single disk refiner.
Paper pulp refiners as described and including the plug or cone type, require the control of the position and spacing of the relatively rotating members, for the purpose of controlling refiner load and for controlling the quality of the refined paper fiber product, among other reasons. A plug type refiner is shown in Staege et al., U.S. Pat. No. 2,666,368, while a control arrangement for a dual inlet disk type refiner is shown in Hayward U.S. Pat. No. 3,506,199.
Traditionally, the control of refiners, resulting in the micrometer movement of one relatively moving refiner element with respect to another, has been accomplished by control systems which have electromechanical drives. While the control of the drives may be electrical or electronic such as shown in Hayward, in response to motor load, changing voltage or power factors, or pulp quality, the ultimate drive is by and through a gear reduction or high ratio mechanical positioning arrangement. In this connection, reference may be had to the Baxter U.S. Pat. No. 2,986,434 which shows a dual inlet radial disk type refiner and the reduction gearing through which the axial position of the stator and rotor elements may be accurately determined and maintained. For proper operation, not only is it necessary to control the relative position of the rotor members, it is also necessary to control the overall spacing between pairs of rotating and stationary refiner plates to compensate for plate wear and/or compensate for bearing wear or other parameters. As noted, such compensations have been made through mechanical or electro-mechanical gear or mechanical reduction type adjustments.
There has been no effective means by which the center of rotation of the rotating member can be shifted, adjusted or compensated in use except by making major set up changes in the alignment of the components. Accordingly, precise geometric control over and between the running relation of the rotary to the stationary member has never been fully available, during operation. Typically, while new refiners are manufactured to plus or minus 1 or 2 thousandths of an inch total run out or tolerance, most of these refiners actually run from 10 up to 20 or more thousandths of an inch out of alignment. Such non-alignment results in a reduction of pulp quality. Also, it is current practice in double disk refiners to allow the rotor to float and find its own position between non-rotating or stator elements. The success of such arrangements depends upon a maintenance of hydraulic balance but, from a practical point of view, such rotors tend to hunt back and forth between limit positions in which the rotor elements may come into actual contact with the stator refining elements.